If you're going hiking or camping this summer, don't get caught without power for your phone. Today, you can get RavPower's 15,000mAh portable solar charger for $15, the all-time low and way, way down from the usual $34. To get the sale price, click the $10 off coupon on the product page and use the code GRORJGCU at checkout.
This charger features a large solar panel area to suck up the sun and keep the battery topped up. It takes at least a week to go from zero to a full charge using only sunlight, however, because of the battery pack's massive 15,000mAh capacity. That's why it also includes a microUSB port for charging with a 5 volt, 2 amp wall charger. Then you can top up two devices simultaneously using sunlight when you're out in the field.
In addition to acting as a battery pack, this portable charge has a flashligh. It's also splashproof, shockproof, and dustproof. RavPower says this nifty little charger can top up an iPhone 7 4.2 times, an iPhone 7 Plus three times, or a Galaxy S8 2.8 times. Those were new phones when this device was released, but sufficed to say it will keep newer phones charged multiple times.